Crude protein and amino acid (
AA
) content in rearing diets affect body composition and reproductive performance. This study evaluated the effects of 4 dietary AA levels during rearing on BW, egg production and composition, fertility, hatchability, and embryo mortality up to 65 wk of age on Cobb 500 slow-feathering (
SF
) broiler breeders. The treatments consisted in 80% (low-AA), 90% (moderate-AA), 100% (standard-AA), and 110% (high-AA) of the AA recommendations for Cobb 500 SF pullets from 5 to 24 wk. AA was guided by an ideal protein profile based on digestible Lys. A total of 1,360 pullets and 288 Cobb MV cockerels were randomly placed in 16 pullets and 16 cockerel floor-pens. At 22 wk, 1,040 females and 112 males were transferred into 16-floor pens in a laying house. BW increased linearly (
P
< 0.01) as AA augmented at 25, 36, and 40 wk. No effects (
P
> 0.05) at the onset of lay were observed. Moderate-AA and standard-AA resulted in the best hen-housed egg production (
HHEP
) at 65 wk with 174.3 and 176.5 eggs, respectively. The optimum level of AA for HHEP at 65 wk was estimated (
P
< 0.001) in 96.7% and 94.7% by the quadratic and broken line models, respectively. Overall, the lightest egg weight (
P
= 0.022) was obtained with 89%AA during rearing, and the heaviest eggs (
P
< 0.001) were found at 54 wk. Response surface regression indicated linear effects on albumen and yolk percentages (
P
< 0.01) increasing and decreasing, respectively, as AA levels augmented; consequently, AA had a negative linear effect on Y:A ratio (
P
= 0.004) with quadratic effects (
P
< 0.01) of age (R
2
= 0.92). No statistical effect of treatments was observed in fertility (
P
> 0.05), but AA had a quadratic effect (
P
= 0.046) on hatchability up to 50 wk of age with 97% as optimum, and decreased linearly (
P
= 0.004) from 51 to 65 wk. A few effects of treatments (
P
< 0.05) on embryo mortality were observed. In conclusion, AA levels during rearing affect broiler breeder reproductive performance.
Drying temperature (
DT
) of corn can influence its nutritional quality, but whether this is influenced by endosperm hardness is not clear. Two parallel experiments were conducted to investigate the effects of 2 yellow dent corn hybrids with average and hard kernel hardness, dried at 3 temperatures (35, 80, and 120°C), and 2 supplementation levels of an exogenous amylase (0, 133 g/ton of feed) on live performance, starch and protein digestibility, and energy utilization of Ross 708 male broilers. Twelve dietary treatments consisting of a 2 × 3 × 2 factorial arrangement were evaluated using 3-way ANOVA in a randomized complete block design. In Experiment 1, a total of 1,920 male-chicks were randomly allocated to 96 floor pens, whereas 480 day-old chicks were distributed among 96 cages for Experiment 2. At 40 d, interaction effects (
P
< 0.05) were detected on BWG, FCR, and flock uniformity. Supplementation with exogenous amylase resulted in heavier broilers, better FCR and flock uniformity, only in the diets based on corn dried at 35°C. Additionally, interaction effects were observed on FCR due to kernel hardness and DT (
P
< 0.01), kernel hardness and amylase supplementation (
P
< 0.001), and DT and amylase supplementation (
P
< 0.05). Exogenous amylase addition to the diets based on corn with an average hardness improved FCR up to 2 points (1.49 vs. 1.51 g:g) whereas there was no effect of amylase on FCR of broilers fed diets based on corn with hard endosperm. Total tract retention of starch was increased (
P
< 0.05) in broilers fed diets based on corn with average kernel hardness compared to hard kernel. Corn dried at 80 and 120°C had up to 1.21% points less starch total tract retention than the one dried at 35°C. Supplementing alpha-amylase resulted in beneficial effects for broiler live performance, energy utilization, and starch total tract digestibility results. Treatment effects on starch characteristics were explored. Corn endosperm hardness, DT and exogenous amylase can influence the live performance of broilers. However, these factors are not independent and so must be manipulated strategically to improve broiler performance.
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